This invention relates to method and apparatus for drilling a borehole into the sapwood of a tree and injecting a chemical solution into the borehole. This invention relates particularly to mobile apparatus for injecting a quantity of solution proportional to the volume of the borehole into a growing pine tree immediately after a borehole is formed therein, to chemically induce the formation of lightwood, rich in oleoresin content.
2. Description of the Prior Art
It has long been known in the art that trees may be injected with appropriate liquids, for example, to supply nutrients to the tree or treat the tree for disease. A number of approaches have been disclosed for preparing a treatment site through the bark of a tree trunk. For example, treatment sites have been prepared by removing a small section of bark to expose sapwood; or by boring a small downwardly sloping hole into the sapwood. Application of a solution of treating chemical to the above treatment sites is made by any convenient means, such as, for example, by use of a sprayer or a brush. With regard to the treatment site prepared by boring a downwardly sloping hole into the sapwood, the solution is applied by pouring it into the hole.
Another method of treatment site preparation comprises providing on the sapwood of a living conifer anywhere from ground level to a height of about 10 ft. above ground level at least one elongated, downwardly sloping hole and subsequently inserting into the hole an absorbent fibrous material for receipt of a treating chemical. The treating chemical will usually be applied in the form of a solution thereof in a suitable solvent, water preferably. The absorbent fibrous material functions as a wick and provides for movement of the solution of treating chemical into the conifer. If desired, the treating chemical, alone or in solution, can be applied to the absorbent fibrous material prior to insertion of the fibrous material into the prepared hole. This method of treatment site preparation is disclosed in U.S. Pat. No. 3,971,159 of July 27, 1976, reference to which is hereby made.
The prior art also discloses another two-step operation wherein a borehole must first be drilled a suitable depth into the tree trunk, after which a nozzle is inserted in the borehole and attached to the tree in a leak-proof manner. In such prior devices, the borehole is of a slightly larger diameter than the nozzle in order that fluid emitted from the nozzle may fill the borehole, thereby obtaining a maximum area for absorption of the liquid by the capillary system of the tree. The making of a leak-proof connection between the nozzle and the borehole frequently resulted in air being trapped in the borehole about the nozzle. Such trapped air is objectionable because it tends to close the pores and passageways in the substance of the tree and to retard and delay the proper diffusion and transfer of the liquid from the point of introduction to remote parts of the tree.
A modification of the aforementioned approach required that the diameter of the initial hole drilled into the trunk would be slightly smaller than the outer diameter of the threaded nozzle tip. A second hole or counterbore having a diameter substantially equal to the nozzle head or sealing ring (if provided) would then be added to insure that when the output orifices in the nozzle shank reached the sapwood, the nozzle would be sealed. The counterbore facilitated sealing by enabling a sealing ring of the inwardly directed nozzle head surface portion to firmly seat against the wood. Following the drilling operation, the hole would be cleaned out in order to insure that the nozzle output orifices could reach the sapwood and that the nozzle head would be adequately sealed without interference from loose wood particles. In many instances, it was necessary to hammer the treatment head into the hole to insure a proper fit for the pressurized injection process thereby often damaging the treatment head, as well as being a time consuming task.
The chemical applicator nozzle disclosed in U.S. Pat. No. 3,968,594 includes a socket and an integral tapered shank portion having output orifices at its tip. The taper of the shank, together with exterior threads provided thereon, facilitates self-tapping and self-sealing of the nozzle. In this apparatus, the threads of the nozzle shank, rather than the inwardly directed surface of the nozzle head or separate sealing ring, provides the sealing. This reference also discloses a method including two separate operations wherein initially a hole is drilled into the sapwood and then a nozzle is inserted therein. Pressurized chemicals are then applied through the nozzle into the sapwood. This method also requires that the nozzle threadably engage the outer surface of the tree.